Senior Full-Stack Engineer — Application Security

Simulation 95; Menlo Park (CA); Hybrid; USD 180,000 - 240,000; Full time

Job summary

Simulation95 in Menlo Park is seeking a senior software engineer to build applications that support expert onboarding, data collection, document handling, review, and delivery across frontend, backend, APIs, and databases.

Security is central: you will implement authentication, authorization, secure sessions, and controls to protect customer and project data, with automated tests and code reviews as part of the workflow.

Qualifications

• Experience shipping and maintaining production applications across the full stack.
• Strong back-end development skills, including API design, relational databases, background processing, and third-party integrations.
• Experience implementing authentication and server-side authorization, with tests that prevent access to another user's or customer's data.
• Practical knowledge of injection, cross-site scripting, broken access controls, unsafe external requests, and other web app vulnerabilities.
• Experience deploying and troubleshooting cloud applications.
• Ability to work independently, explain technical tradeoffs, and communicate with technical and nontechnical colleagues.

Responsibilities

• Develop product features across user interfaces, back-end services, data models, and integrations.
• Implement authentication, authorization, secure sessions, and appropriate separation of customer, project, and user data.
• Build secure workflows for uploading, processing, storing, sharing, and deleting documents and data.
• Review designs and code for security weaknesses, explain their impact, and implement fixes.
• Add automated tests, dependency checks, secret scanning, and security checks to development and release workflows.
• Improve monitoring, audit trails, error handling, and recovery while keeping sensitive information out of logs.
• Investigate production failures, address vulnerabilities, improve performance, and document technical decisions.

Skills

Full stack

API design

Auth & security

Cloud deployments

Independent worker

Job description

Location Menlo Park, CA (San Francisco Bay Area)

Working arrangement Hybrid

About Simulation95

Simulation95 is building at the intersection of artificial intelligence, healthcare, and life sciences. We believe meaningful progress starts with people who understand the hardest problems firsthand. We're bringing together experts, researchers, and builders to turn that understanding into technology that matters.

For curious people who take their craft seriously, this is an opportunity to help shape something early- with challenging problems, meaningful responsibility, and room to make a lasting contribution.

About the role

You will build the applications that support expert onboarding, data collection, document handling, review, and delivery. Your work will span the front end, back end, APIs, and databases, from initial design through production.

Application security is central to this role. The software handles sensitive information and proprietary work, so access controls, data handling, and security testing must be part of everyday engineering decisions. This is a senior individual contributor position with responsibility for architecture, implementation, and product quality.

Responsibilities

• Develop product features across user interfaces, back-end services, data models, and integrations.
• Implement authentication, authorization, secure sessions, and appropriate separation of customer, project, and user data.
• Build secure workflows for uploading, processing, storing, sharing, and deleting documents and data.
• Review designs and code for security weaknesses, explain their impact, and implement fixes.
• Add automated tests, dependency checks, secret scanning, and security checks to development and release workflows.
• Improve monitoring, audit trails, error handling, and recovery while keeping sensitive information out of logs.
• Investigate production failures, address vulnerabilities, improve performance, and document technical decisions.

Qualifications

• Experience shipping and maintaining production applications across the full stack.
• Strong back-end development skills, including API design, relational databases, background processing, and third-party integrations.
• Experience implementing authentication and server-side authorization, including tests that prevent access to another user's or customer's data.
• Practical knowledge of injection, cross-site scripting, broken access controls, unsafe external requests, and other web application vulnerabilities.
• Experience deploying and troubleshooting cloud applications.
• Ability to work independently, explain technical tradeoffs, and communicate with technical and nontechnical colleagues.

Preferred experience

• Applications that handle confidential business, research, or health information.
• Enterprise identity integrations, single sign-on, and multifactor authentication.
• Threat modeling, penetration-test remediation, or security-focused code review.
• AI application security, including prompt injection, unintended data exposure, and permission controls for tools connected to models.
• Data provenance, versioning, and workflows with traceable review and approval.